Modifiers are polymeric compositions which are included in a matrix polymer to improve properties such as impact strength. Modifiers have been used to impart toughness and ductility to polyvinyl chloride ("PVC") for extrusion and injection molding applications.
Various types of modifiers for PVC are known in the art. For example, core/shell polymers of methyl methacrylate, butadiene, and styrene ("MBS") have been employed as modifiers to improve the toughness of PVS. MBS polymers, however, do not impart either sufficient weatherability or ultraviolet light resistance to be used in PVC for outdoor applications.
Acrylic core/shell modifers such as those with poly (butyl acrylate) cores, and poly (methyl methacrylate) shells have been employed to impart ultraviolet light resistance to PVC. These acrylic core/shell polymer modifiers, however, generally provide less impact strength than MBS modifiers. Furthermore, acrylic core/shell polymer modifiers impart non-uniform light absorption, known as pearlescence, as well as loss of color depth in pigmented PVC compositions.
A need therefore exists for modifers which have weatherability and ultraviolet light resistance which impart improved ductility and toughness to PVC compositions while avoiding disadvantages such as pearlescence and loss of color depth.